CN104583439B - The steel plate of pole excellent in low temperature toughness - Google Patents
The steel plate of pole excellent in low temperature toughness Download PDFInfo
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- CN104583439B CN104583439B CN201380043453.6A CN201380043453A CN104583439B CN 104583439 B CN104583439 B CN 104583439B CN 201380043453 A CN201380043453 A CN 201380043453A CN 104583439 B CN104583439 B CN 104583439B
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
Abstract
The steel plate of the present invention comprises composition in the steel of regulation, and meet: present in steel plate, equivalent circle diameter is less than 1.8 more than the average roundness A of the field trash of 1.0 μm, volume fraction (V) 196 DEG C of retained austenite phases existed is 2.0～12.0%, and the B value represented by following (1) formula is more than 1.3.B=V2/3/A···(1)。
Description
Technical field
The present invention relates to the steel plate of pole excellent in low temperature toughness, in detail, even if relate to Ni content reduce to 5.0～
About 7.5%, the thickness that toughness [the particularly toughness of plate width direction (C direction)] under the extremely low temperature below-196 DEG C is the best
Steel plate.Hereinafter, (representational to have storage tank, fortune towards the steel plate of the liquefied natural gas (LNG) exposed to the open air under above-mentioned extremely low temperature
Defeated ship etc.) centered by illustrate, but the steel plate of the present invention is not limited to this meaning, but is suitable for exposing to the open air
Whole steel plates of the use in the purposes under extremely low temperature below-196 DEG C.
Background technology
For the LNG tank steel plate of the storage tank of liquefied natural gas (LNG), in addition to requiring high intensity, also require have
Can tolerate the high tenacity of the extremely low temperature of-196 DEG C.Up to now, as the steel plate for such use, use containing
The steel plate of the Ni (9%Ni steel) of about 9%, but in recent years, because the cost increase of Ni, even so less than 9%
Under low Ni content, the exploitation of the steel plate that pole low-temperature flexibility is still excellent is advanced.
Such as, non-patent literature 1 describes and coexists the territory heat treatment shadow to the low-temperature flexibility of 6%Ni steel about α-γ two-phase
Ring.In detail, describe and coexist the heat treatment of territory (between Ac1～Ac3) by being applied to α-γ two-phase before temper
(L process), it is possible to give with the 9%Ni steel processed by common Q-tempering on an equal basis above, the extremely low temperature of-196 DEG C
Toughness；This heat treatment also makes the toughness of C direction (plate width direction) test film improve；These effects be due to substantial amounts of fine and
Still keep the existence of stable retained austenite to produce under extremely low temperature for shock loading, etc..But, according to above-mentioned side
Method, although the pole excellent in low temperature toughness of rolling direction (L direction), but there is the extremely low temperature Toughness Ratio L of plate width direction (C direction)
The tendency of direction difference.It addition, there is no the record of brittle fracture rate.
Technology as above-mentioned non-patent literature 1 is also documented in patent documentation 1 and patent documentation 2.Wherein, patent literary composition
Offer and in 1, recorded following method: the steel that the Ni containing 4.0～10%, austenitic grain size etc. are controlled in prescribed limit
After carrying out hot rolling, it is heated between Ac1～Ac3, is then cooled off, this process (is equivalent to above-mentioned non-patent literature 1 institute
The L process stated) it is repeated once or after more than twice, it is tempered with the temperature below Ac1 transformation temperature.It addition, in patent documentation 2
Describe following method: for the Ni containing 4.0～10%, make the steel that size is below 1 μm of the AlN before hot rolling, carry out with
The heat treatment (L process → temper) that above-mentioned patent documentation 1 is same.The impact value of these described in method-196 DEG C
(vE-196) probably speculating it is L direction, the above-mentioned toughness value in C direction is unclear.It addition, in these methods for intensity not
Give consideration, there is no the record of brittle fracture rate.
It addition, in non-patent literature 2, be combined about by above-mentioned L process (two phase region Quenching Treatment) and TMCP
The exploitation of 6%Ni steel of LNG storage tank recorded.According to the document, although describe the tough of rolling direction (L direction)
Property demonstrates high value, but is silent on the toughness value in plate width direction (C direction).
Patent documentation 3 is recorded a kind of containing 0.3～the Ni of 10% with the Mg of ormal weight, and made containing of regulation particle diameter
The high tenacity high tension steel that Mg oxide particle is the most scattered, more than 570MPa level toughness of welded zone is excellent.Above-mentioned patent
Document 3 is recorded: by making heating austenite particle diameter obtain miniaturization containing the control of Mg oxide, mother metal and welding heat affected
The toughness in portion (HAZ) improves；To this end, deoxidant element add before O (oxygen) amount and the order of addition of Mg and other deoxidant element
Critically important, soluble oxygen content be 0.001～0.02% steel-making in add Mg, Ti, Al simultaneously after, carry out casting and becoming steel
Base, or when adding Mg, Ti, Al, after finally adding Al, then carry out casting and becoming steel billet.Enforcement at above-mentioned patent documentation 3
Example is recorded the toughness value (fracture transition temperature vTrs) in C direction, the good (fracture transition temperature of the above-mentioned characteristic of 9%Ni steel
VTrs≤-196 DEG C), but the above-mentioned characteristic of the Ni steel of 5% neighborhood is-140 DEG C, it is desirable to improve further.
And then, patent documentation 4 records following technology: make the distribution of austenite equal by adding the Ni of 5.0～7.5%
Homogenize, thus obtain the toughness (CTOD characteristic) of mother metal and welding point, stress, the unstable thickness destroying rejection characteristic excellence
Steel plate.But, the evaluation temperature in CTOD test is-165 DEG C, slightly higher, is not the public affairs of the extremely low temperature towards less than-196 DEG C
Open technology.Even if additionally, scrutinize patent documentation 4, also entirely without the record of the brittle fracture rate in Charpy impact suction test.
Additionally, in order to manufacture the steel plate described in patent documentation 4, it is necessary to carry out before hot rolling at 1250～1380 DEG C 8～50 hours
Long-time heating under this high temperature processes, and is disadvantageous from the viewpoint of manufacturing cost.
Prior art literature
Patent documentation
Patent documentation 1: Japanese Laid-Open Patent Publication 49-135813 publication
Patent documentation 2: Japanese Laid-Open Patent Publication 51-13308 publication
Patent documentation 3: Japanese Unexamined Patent Publication 2001-123245 publication
Patent documentation 4: No. 4975888 publications of Japanese Patent No.
Non-patent literature
Non-patent literature 1: vow wild etc., " the low temperature properties To of 6%Ni and Pot The α-γ two-phase coexist the shadow of territory reason
" (α-γ two-phase coexist territory heat treatment bring the impact of low-temperature flexibility of 6%Ni steel), ferrum and steel, the 59th year (1973) the 6th
Number, p752～763
Non-patent literature 2: Gu Gu etc., " L N G タ Application Network 6%Ni's " (opening of LNG storage tank 6%Ni steel
Send out), CAMP-ISI J, Vol.23 (2010), p1322
Summary of the invention
The problem that invention is to be solved
As it has been described above, up to now, Ni content be 5.0～about 7.5% Ni steel in, although the extremely low temperature of-196 DEG C
The technology of tenacity excellent is suggested, but the pole low-temperature flexibility in C direction is not well studied.Particularly it is strongly required
Extremely low temperature under (in detail, tensile strength TS ＞ 690MPa, yield strength YS ＞ 590MPa) high intensity that strength of parent is high
The raising further (the pole low-temperature flexibility in C direction improves) of toughness.
It addition, in the above documents, not about the research of brittle fracture rate.Brittle fracture rate is to represent at Charpy impact
The ratio of produced brittle break during imposed load in test.At the position that there occurs brittle break, till destroying, steel
The energy that material is absorbed significantly diminishes, and destroys easily development, therefore especially for the destruction of the extremely low temperature of suppression, by the general summer
The brittle fracture rate suppression occurred in Charpy test is extremely important condition in low-level (less than 10%).But, because
Intensity is the highest, and brittle break is more susceptible to, so realizing brittle fracture rate≤10% under high strength of parent as described above
It is usually difficulty.Therefore, in the high-strength steel plate that strength of parent is high, the technology possessing these two aspects not yet proposes.
The present invention makes in view of the foregoing, its object is to provide a kind of high-strength steel plate, and it contains at Ni
Amount be 5.0～about 7.5% Ni steel in, it is possible to realize pole low-temperature flexibility (the extremely low Wen Ren in particularly C direction of-196 DEG C
Property) excellent, brittle fracture rate≤10%.
For solving the means of problem
Can solve the problem that the steel plate of the pole excellent in low temperature toughness of the present invention of above-mentioned problem, it has following main idea: with matter
Amount % meter is containing C:0.02～0.10%, below Si:0.40% (without 0%), Mn:0.50～2.0%, below P:0.007%
(without 0%), below S:0.007% (without 0%), Al:0.005～0.050%, Ni:5.0～7.5%, N:0.010% with
Under (without 0%), surplus is ferrum and inevitable impurity, and present in steel plate, equivalent circle diameter is more than the field trash of 1.0 μm
Average roundness (A) be less than 1.8 ,-196 DEG C exist retained austenite phases volume fraction (V) meet 2.0～
12.0% and following (1) formula represented by B value be more than 1.3.
B=V2/3/A···(1)
The present invention preferred embodiment in, above-mentioned steel plate is:-196 DEG C exist retained austenites with
Volume fraction meter meets 4.0%～12.0%.
In a preferred embodiment of the invention, above-mentioned steel plate is: possibly together with selected from below Cu:1.00% (without 0%),
Below Cr:1.2% (without 0%), below Mo:1.00% (without 0%), below Ti:0.025% (without 0%), Nb:
Less than 0.10% (without 0%), below V:0.50% (without 0%), below B:0.0050% (without 0%), Ca:0.0030%
At least one (without 0%), in below REM:0.0050% (without 0%), below Zr:0.0050% (without 0%) below.
The effect of invention
In accordance with the invention it is possible to provide a kind of high-strength steel plate, it reduces to 5.0～the low Ni of 7.5% at Ni content
Steel, though strength of parent high (in detail, tensile strength TS ＞ 690MPa, yield strength YS ＞ 590MPa) ,-196 DEG C with
Under pole low-temperature flexibility (the pole low-temperature flexibility in particularly C direction) also excellent, specifically, the Charpy impact in C direction absorbs
In test, meet brittle fracture rate≤10% (brittle fracture rate≤50% of preferably-233 DEG C) of-196 DEG C.
Detailed description of the invention
The present inventor etc. are studied to provide following pole low-temperature flexibility to develop skill, i.e. subtracted at Ni content
Few to less than 7.5% and meet in the high-strength steel plate of tensile strength TS ＞ 690MPa, yield strength YS ＞ 590MPa, at C
In the charp impact value in direction, meet brittle fracture rate≤10% of-196 DEG C.It is it was found that will be at-196 DEG C about (a)
The volume fraction V of retained austenite (residual γ) phase existed control 2.0～12.0% [be preferably controlled to 4.0%～
12.0% (volume fraction)] and (b) for encourage brittle break development equivalent circle diameter more than 1.0 μm field trash (with
Under, sometimes it is only called field trash.), the average roundness A of above-mentioned field trash is being reduced to less than 1.8 and by following (1) formula
Shown B value can reach desired purpose when controlling more than 1.3, thus completes the present invention.
B=V2/3/A···(1)
The characteristic particularly should write volumes about in the relation of aforesaid prior art, is the latter (b).With
Under, illustrate for reaching the process of the present invention.
The present inventor etc. are in order to provide the most excellent the pole low-temperature flexibility of-196 DEG C in the Ni steel that Ni content is less than 7.5%
Different steel plate and repeatedly study.Specifically, in the present invention, from providing brittle fracture rate≤10% meeting C direction, resisting
Tensile strength TS ＞ 690MPa, the high-strength steel plate of pole excellent in low temperature toughness of complete characteristic of yield strength YS ＞ 590MPa
Viewpoint is set out, first, and the method shown in research document described in prior art.
Above-mentioned document is pointed out, in order to improve the pole low-temperature flexibility of 5%Ni steel, it is important that make-196 DEG C of existence
Retained austenite (residual γ) stabilisation.If it addition, consider manufacture method, then it is recommended that in the steel-making stage, control de-
Oxygen element add before soluble oxygen content, last in this steel-making add Al and cast, and coexist territory in α-γ two-phase
After the heat treatment (L process) of (between Ac1～Ac3), the method carrying out temper with the temperature below Ac1 transformation temperature, thus
Enlightenment has pole low-temperature flexibility to improve.But, according to the result of study of the present inventor etc., although knowing L side when utilizing said method
To pole low-temperature flexibility improve, but the pole low-temperature flexibility in C direction is insufficient, it is impossible to realize the above-mentioned mesh of prompting in the present invention
Mark rank (brittle fracture rate≤10% in C direction).
Having carried out the most further repeatedly studying, result is known, in order to obtain the thick steel of desired pole excellent in low temperature toughness
Plate, it is necessary to substantially follow above-mentioned technology, while add feature further in steel plate and manufacture method thereof.In detail
Saying, (i), in steel plate, makes the volume fraction V of the residual γ phase at-196 DEG C exist in the range of V=2.0～12.0%,
In addition, it is conceived to the equivalent circle diameter distinguishing the development the encouraging brittle break field trash more than 1.0 μm, by above-mentioned folder
The average roundness A of foreign material reduces to less than 1.8, and would indicate that the average roundness A of above-mentioned field trash and-196 DEG C of existence
Above-mentioned residual γ phase volume fraction V (%) relation the B value shown in formula (1) control be B value >=1.3, this is effective；
(ii) in order to manufacture such steel plate, the control of soluble oxygen content (free O amount) before adding except the Al in steel-making stage, hot rolling
After Ac1～Ac3 between heat treatment (L process) → set point of temperature region temper beyond, the further control in steel-making stage
It is shaped with effect, controls (to be positioned at 1/2 of slab thickness t below 300 seconds the cool time (t1) of 1450～1500 DEG C during by casting
The value put) and control (to be positioned at the 1/4 of slab thickness t below 680 seconds by the cool time (t2) of 1300～1200 DEG C during casting
The value of position) effectively.
Furthermore, it was found that (c) is in above-mentioned (a), by the residual γ phase controls-196 DEG C of existence 4.0%～12.0%
(volume fraction), even if at-233 DEG C of more low temperature, it is also possible to brittle fracture rate is maintained at the good level of less than 50%,
D (), in order to manufacture such steel plate, after hot rolling, carries out the stipulated time in the heat treatment (L process) between Ac1～Ac3
Holding is effective, thus completes the present invention.
In this manual, so-called " pole excellent in low temperature toughness ", is to survey according to the method described in embodiment hurdle described later
When determining the brittle fracture rate in the Charpy impact absorption test in C direction (plate width direction), the brittle fracture rate of satisfied-196 DEG C≤
10%.In embodiment described later, although the brittle fracture rate of L direction (rolling direction) cannot measure, if but it is based on C
The brittle fracture rate in direction below 10%, then the brittle fracture rate in L direction also inevitable such empirical law below 10%.
In this specification, " steel plate " refers to the thickness substantially 6～50mm of steel plate.
The most in the present invention, to meet tensile strength TS ＞ 690MPa, the high-strength thick of yield strength YS ＞ 590MPa
Steel plate is object.
Hereinafter, the steel plate for the present invention is described in detail.
As it has been described above, the steel plate of the present invention, it is characterised in that its be in terms of quality % containing C:0.02～0.10%,
Below Si:0.40% (without 0%), Mn:0.50～2.0%, below P:0.007% (without 0%), below S:0.007% are (no
Containing 0%), Al:0.005～0.050%, Ni:5.0～7.5%, below N:0.010% (without 0%), surplus is ferrum and can not
The steel plate of the impurity avoided, equivalent circle diameter more than the average roundness (A) of the field trash of 1.0 μm is present in steel plate
Less than 1.8, the volume fraction (V)-196 DEG C of retained austenite phases existed meets 2.0～12.0%, and following (1) formula institute
The B value represented is more than 1.3.
B=V2/3/A···(1)
Illustrate firstly, for composition in steel.
C:0.02～0.10%
C is to ensure that the necessary element of intensity and retained austenite.In order to effectively play such effect, make under C amount
It is limited to more than 0.02%.The preferred lower limit of C amount is more than 0.03%, more preferably more than 0.04%.But, if add superfluously
Adding, then cause pole low-temperature flexibility to reduce due to excessively rising of intensity, therefore making its upper limit is less than 0.10%.It is preferred that C measures
The upper limit is less than 0.08%, more preferably less than 0.06%.
Below Si:0.40% (without 0%)
Si is the element useful as deoxidation material.But, if add superfluously, then the generation of the island-like martensite phase of hard
Being promoted, pole low-temperature flexibility reduces, and therefore making its upper limit is less than 0.40%.The preferred upper limit of Si amount is less than 0.35%,
More preferably less than 0.20%.
Mn:0.50～2.0%
Mn also works as deoxidation material, is austenite (γ) stabilizing element, contributes to increase the unit of residual γ amount
Element.In order to effectively play such effect, the lower limit making Mn measure is 0.50%.The preferred lower limit of Mn amount is more than 0.6%, more
It is preferably more than 0.7%.But, if add superfluously, then cause temper embrittlement, it is impossible to guarantee desired pole low-temperature flexibility, because of
This makes its upper limit be less than 2.0%.The preferred upper limit of Mn amount is less than 1.5%, more preferably less than 1.3%.
Below P:0.007% (without 0%)
P is the impurity element of the reason constituting intercrystalline failure, in order to ensure desired pole low-temperature flexibility so that it is the upper limit is
Less than 0.007%.The preferred upper limit of P amount is less than 0.005%.P amount is the fewest more good, but the industrial P of making amount is 0% to have any problem.
Below S:0.007% (without 0%)
S also with above-mentioned P again it is constitute the impurity element of reason of intercrystalline failure, in order to ensure desired extremely low Wen Ren
Property so that it is the upper limit is less than 0.007%.Shown in embodiment as be described hereinafter, if S quantitative change is many, then brittle fracture rate increases, it is impossible to real
Existing desired pole low-temperature flexibility (brittle fracture rate≤10% of-196 DEG C).The preferred upper limit of S amount is less than 0.005%.If S
Amount is few, the fewest more good, but the industrial S of making amount is 0 to have any problem.
Al:0.005～0.050%
Al is deoxidant element.If the content of Al is not enough, then the free oxygen concentration in steel-making rises, in the process of casting cooling
In, the surface recombination of the field trash in being originally present in steel-making generates oxide or these secondary inclusion things of sulfide, thus
The shape of field trash changes, and equivalent circle diameter becomes big, therefore by its lower limit more than the average roundness of the field trash of 1.0 μm
It is set to more than 0.005%.The preferred lower limit of Al amount is more than 0.010%, more preferably more than 0.015%.But, if surplus adds
Adding, the coagulation of the most above-mentioned field trash, zoarium are promoted, and the average roundness of this field trash still becomes big, therefore its upper limit is set
It is less than 0.050%.The preferred upper limit of Al amount is less than 0.045%, more preferably less than 0.04%.
Ni:5.0～7.5%
Ni is for guaranteeing necessary element for pole low-temperature flexibility improves useful retained austenite (residual γ).
In order to effectively play such effect, the lower limit making Ni measure is more than 5.0%.The preferred lower limit of Ni amount is more than 5.2%, more
It is preferably more than 5.4%.But, if add superfluously, then the cost causing raw material is high, and therefore making its upper limit is less than 7.5%.
The preferred upper limit of Ni amount is less than 7.0%, more preferably less than 6.5%, more preferably less than 6.0%.
Below N:0.010% (without 0%)
N makes pole low-temperature flexibility reduce due to strain-aging, and therefore making its upper limit is less than 0.010%.Preferably going up of N amount
It is limited to less than 0.006%, more preferably less than 0.004%.
The steel plate of the present invention contains mentioned component as basis, and surplus is ferrum and inevitable impurity.
In the present invention, for the purpose of giving characteristic further, it is possible to containing following selection component.
Below Cu:1.00% (without 0%)
Cu is γ stabilizing element, contributes to remain the element of the increase of γ amount.In order to effectively play such work
With, preferably make Cu contain more than 0.05%.But, if add superfluously, then cause the excessive raising of intensity, can not get desired
Pole low-temperature flexibility effect, the most preferably making its upper limit is less than 1.00%.The more preferably upper limit of Cu amount is less than 0.8%, enters one
Step is preferably less than 0.7%.
At least one in below Cr:1.2% (without 0%) and below Mo:1.00% (without 0%)
Cr and Mo is all that intensity improves element.These elements can individually add, it is also possible to two kinds and use.In order to effectively
Playing above-mentioned effect, preferably making Cr amount is more than 0.05%, and making Mo amount is more than 0.01%.But, if add superfluously, then lead
Causing the excessive raising of intensity, it is impossible to guarantee desired pole low-temperature flexibility, therefore the preferred upper limit of Cr amount is less than 1.2% (more excellent
Elect less than 1.1% as, more preferably less than 0.9%, the most preferably less than 0.5%), the preferred upper limit of Mo amount is
Less than 1.00% (more preferably less than 0.8%, more preferably less than 0.6%).
(do not contain selected from below Ti:0.025% (without 0%), below Nb:0.10% (without 0%) and below V:0.50%
0%) at least one in
Ti, Nb and V, all as Carbonitride Precipitation, are the elements making intensity increase.These elements can individually add, also
Can be two or more and use.In order to effectively play above-mentioned effect, preferably making Ti amount is more than 0.005%, makes Nb measure and is
More than 0.005%, making V amount is more than 0.005%.But, if add superfluously, then cause the excessive raising of intensity, it is impossible to really
Protect desired pole low-temperature flexibility, therefore the preferred upper limit of Ti amount be less than 0.025% (more preferably less than 0.018%, further
Be preferably less than 0.015%), the preferred upper limit of Nb amount be less than 0.10% (more preferably less than 0.05%, more preferably
Less than 0.02%), the preferred upper limit of V amount be less than 0.50% (more preferably less than 0.3%, more preferably 0.2% with
Under).
Below B:0.0050% (without 0%)
B is to be improved by hardenability and contribute to the element that intensity improves.In order to effectively play above-mentioned effect, preferably make
B amount is more than 0.0005%.But, if add superfluously, then bring the excessive raising of intensity, it is impossible to guarantee desired extremely low temperature
Toughness, the preferred upper limit therefore making B measure be less than 0.0050% (more preferably less than 0.0030%, more preferably
Less than 0.0020%).
Selected from below Ca:0.0030% (without 0%), REM (rare earth element): less than 0.0050% (without 0%) and
At least one in below Zr:0.0050% (without 0%)
Ca, REM and Zr are all deoxidant elements, and by adding these elements, the oxygen concentration in steel reduces, the amount of oxide subtracts
Few, thus toughness is brought and affects.These elements can individually add, it is also possible to two or more and use.In order to effectively send out
Waving above-mentioned effect, preferably making Ca amount is more than 0.0005%, and (REM set forth below is individually containing sometimes for individually to contain to make REM amount
Amount, containing time two or more being its total amount.Hereinafter, about REM amount all with.) be more than 0.0005%, make Zr amount be
More than 0.0005%.But, if add superfluously, then the size of oxide increases, and pole low-temperature flexibility reduces, and therefore makes Ca measure
Preferred upper limit is less than 0.0030% (more preferably less than 0.0025%), and the preferred upper limit of REM amount is less than 0.0050% (more
It is preferably less than 0.0040%), the preferred upper limit of Zr amount is less than 0.0050% (more preferably less than 0.0040%).
In this manual, REM (rare earth element) is that lanthanide series is (in periodic chart, from the La of atom sequence number 57 to former
15 kinds of elements of the Lu of sub-sequence number 71) plus Sc (scandium) and the groups of elements of Y (yttrium), its can be used alone or two or more also
With.Preferably rare earth element is Ce, La.The interpolation form of REM is not particularly limited, can be to mainly contain the mixing of Ce and La
The form of rare earth (such as Ce: about about 70%, La: about 20～about 30%) is added, it is also possible to add Ce, La etc. individually.
Above, composition in the steel of the present invention is illustrated.
Additionally, the steel plate of the present invention, the volume fraction V-196 DEG C of residual γ phases existed meet 2.0～
12.0% (preferably 4.0～12.0%).
Known in the raising contributing to pole low-temperature flexibility at-196 DEG C of residual γ existed.Such in order to effectively play
Effect, making the volume fraction V remaining γ phase shared in-196 DEG C of whole tissues existed is more than 2.0%.But, remain γ
Compared with matrix, the most soft, if residual γ quantitative change obtains superfluous, then cannot ensure the value that YS is regulation, therefore make its upper limit
It is 12.0% (with reference to the No.43 of table 2B described later).About the volume fraction V of residual γ phase, preferred lower limit is more than 4.0%,
More preferably lower limit is more than 6.0%, and preferred upper limit is less than 11.5%, and the more preferably upper limit is less than 11.0%.
Additionally, control more than 4.0% by remaining the volume fraction shared by γ in-196 DEG C of whole tissues existed, from
And, even at-233 DEG C than above-mentioned-196 DEG C more low temperature, it is also possible to brittle fracture rate is maintained at less than 50%
Good level.More preferably lower limit when wishing to play further such effect is more than 6.0%, the preferred upper limit and above-mentioned phase
With.
It should be noted that in the steel plate of the present invention, among-196 DEG C of tissues existed, the volume of residual γ phase
The control dividing rate V is critically important, for other the tissue beyond residual γ, does not then have any restriction, as long as logical in steel plate
The tissue being commonly present.As the tissue beyond residual γ, such as, the carbides such as bainite, martensite, cementite can be enumerated
Deng.
And then, in the steel plate of the present invention, about equivalent circle diameter present in steel plate more than the field trash of 1.0 μm, on
The average roundness A stating field trash meets the B value represented by A≤1.8 and following (1) formula satisfied more than 1.3.
B=V2/3/A···(1)
It is the size being conceived to above-mentioned field trash at this " equivalent circle diameter ", tries to achieve suppose with the circle of its area equation straight
Footpath.
Here, the most why be conceived to the equivalent circle diameter field trash more than 1.0 μm, it is because distinguishing above-mentioned
Field trash encourages the development of brittle break.That is, in order to while guaranteeing the high intensity of regulation, improve the fragility under extremely low temperature and break
Split rate, it is desirable to reduce encourage the field trash of brittle break, according to the result of study of the present inventor etc., if above-mentioned field trash
Average roundness A becomes big, even if controlling in above-mentioned scope by the volume fraction V of the residual γ phase of-196 DEG C, can not realize wishing
The pole low-temperature flexibility (with reference to No.33,35,36 of table 2B described later) hoped.The average roundness A of above-mentioned field trash is the smaller the better,
It is preferably less than 1.7, more preferably less than 1.5, most preferably 1.It should be noted that in the present invention, equivalent circle diameter surpasses
Cross below average-size (leveled circular equivalent diameter) substantially 2.0 μm of the field trash of 1.0 μm.
Above-mentioned field trash can be measured with the method described in embodiment described later.Here, equivalent circle diameter is more than 1.0
The kind of " field trash " in the field trash of μm, is not particularly limited in the present invention.This is the generation shadow due to brittle break
Ring maximum is not the kind of field trash, but the size of field trash (equivalent circle diameter).As the kind of above-mentioned field trash, example
As, in addition to can enumerating the individually particle such as oxide, sulfide, nitride, oxynitride, also can be enumerated these independent
The two or more compound complex of particle thing, or the compound particle etc. that these single particles are combined with other element.
By equivalent circle diameter being set to more than the average roundness A of the thick field trash of 1.0 μm as the present invention
Less than 1.8 so that it is guaranteed that the mechanism that the intensity of regulation and pole low-temperature flexibility improve specifically is failed to understand, but is presumed as follows.Field trash
Hardness is typically high than matrix, is therefore susceptible to stress and concentrates, as a result of which it is, mostly played the work of the starting point of brittle break
With.Now, owing to the change of shape of field trash is the most serious, exacerbate the stress around field trash the most locally and concentrate, and then
Easily induce brittle break.Therefore speculate, [that is, the average roundness A of above-mentioned field trash is controlled if the field trash of deformation reduces
With as far as possible close to positive round (A=1) below 1.8], then it can be avoided that the generation of stress concentration, pole low-temperature flexibility then improves.
And then, in the present invention, not only need to control the average roundness A of above-mentioned field trash, it is necessary to make above-mentioned (1) formula institute
The B value represented meets B value >=1.3.
Above-mentioned B value is the parameter of the brittle fracture rate for reducing extremely low temperature, as shown in above-mentioned (1) formula, for by above-mentioned
The average roundness A of field trash and calculating in the relation of the volume fraction V of-196 DEG C of retained austenites existed (residual γ) phase
Value.Derivation to above-mentioned B value is passed through and is illustrated below.
The starting point of known brittle break is the most, the biggest to the least then brittle fracture rate of development resistance of brittle break.Typically
For, thick field trash easily becomes the starting point of brittle break, and the present inventor etc. verifies, and the roundness of thick field trash is more
Greatly, in other words the degree deviateing positive round (A=1) and deform is the most serious, and the easiest starting point as brittle break works；Enter
And, residual γ the most more hinders the development of brittle break.Based on these opinions, utilize real according to the infrastest that quantity is various
Test the two the obtained contribution rate to the brittle fracture rate in extremely low temperature range, found that the B value represented by above-mentioned (1) formula is
For evaluating the useful parameter of pole low-temperature flexibility.As be described hereinafter shown in embodiment, guaranteeing volume fraction V and the circle of residual γ phase
On the basis of equivalent diameter is more than the form (average roundness) of the thick field trash of 1.0 μm, above-mentioned B value is controlled 1.3
Above, the brittle fracture rate taking into account intensity at high level with-196 DEG C and-233 DEG C is achieved first.
Above-mentioned B value is preferably more than 1.6, more preferably more than 1.8.From the viewpoint of the low-temperature flexibility of pole, above-mentioned B value is more
Big the best, limit is not particularly limited on which.But, as it was previously stated, cannot guarantee that YS is when the volume fraction V of residual γ is excessive
The value of regulation, therefore the ceiling restriction by the volume fraction V of residual γ is 12.0%, and now the upper limit actual upper bound of B value is made as
5.2 (=12.02/3/ 1) (in the calculating formula of B value, residual the volume fraction V=12.0% of γ, average roundness A=1 are substituted into).
In view of intensity and tough sexual balance, more preferably B value is less than 3.0.
Below, the manufacture method for the steel plate of the present invention illustrates.
The characteristic of the manufacture method of the present invention, is following (A)～(B).
(A) in the steel-making stage, the free oxygen amount [O] before being added by Al controls at below 100ppm, by 1450 during casting
～cool time (t1) of 1500 DEG C controls (to be positioned at the value of 1/2 position of slab thickness t) below 300 seconds and by during casting
Control the cool time (t2) of 1300～1200 DEG C (to be positioned at the value of 1/4 position of slab thickness t) below 680 seconds.According to above-mentioned
(A) method, particularly can be reduced to prescribed limit by the average roundness A of above-mentioned field trash.
(B) after hot rolling, after the temperature range of Ac1～Ac3 point heats, keeps, carry out water-cooled, then at 520 DEG C～
The temperature range of Ac1 point carries out 10～60 minutes temper, carries out air cooling or water-cooled afterwards.According to the method for above-mentioned (B), special
It not suitably to be controlled at-196 DEG C of volume fractions of residual γ phases existed.
It should be noted that the B value owing to specifying in the present invention is the average roundness about above-mentioned field trash and residual
The parameter of this two side of the volume fraction of γ, so by suitably controlling above-mentioned (A)～(B), it is possible to above-mentioned B value is controlled in regulation
Scope.
For relation with aforesaid prior art, among the method for above-mentioned (A), maximum is characterised by controlling especially t1
And t2.
Hereinafter, each operation is described in detail.
(about melting operation)
In the present invention, the adding method for Al pays particular attention to.This is because, should control in the present invention
Equivalent circle diameter is more than the field trash of 1.0 μm, mainly so that in liquation, the Al system field trash of generation is as starting point, at oxide and sulfur
Composition generation during the secondary inclusion thing cooling of compound etc., but above-mentioned Al system field trash due to coagulation/zoarium easy coarsening,
And easily become the deformed shape that roundness is big.
First, when adding the Al as deoxidation material in steel-making, the free oxygen amount before being added by Al (the most molten is deposited
Oxygen amount, [O] amount.) control at below 100ppm.If [O] amount increases more than 100ppm, then the Al system field trash generated when Al adds
Adding, roundness can exceed the scope (with reference to the No.33 of table 2B described later) of regulation.[O] amount the fewest more good, preferably 80ppm with
Under, more preferably below 50ppm.It should be noted that from the viewpoint of the average roundness controlling above-mentioned field trash, right
The lower limit that [O] measures is not particularly limited.
As controlling the method that [O] measures as described so, such as, the deoxidant element adding Mn, Si can be set forth in steel-making
And the method carrying out deoxidation.When being also added with the deoxidation material of Ti, Ca, REM, Zr etc. in addition to above-mentioned element as selection component,
Even if adding these elements also to be able to control [O] amount.
In order to control Al system field trash, it is important that control [O] amount before Al adds, regardless of Al and other deoxidation unit
The order of addition of element.But, if add Al when [O] measures high, then cause the temperature of steel-making to rise due to oxidation reaction,
Operationally form danger, before Al, the most preferably add Si, Mn.It addition, the above-mentioned selection component of Ti etc., preferably add at Al
Add in steel-making again after adding.
Then, casting is started.Temperature range during casting substantially less than 1650 DEG C, but distinguish in the present invention, special
Not it is important that the cool time (t1) of temperature range by 1450～1500 DEG C controls below 300 seconds and by 1300～1200
DEG C cool time (t2) control below 680 seconds, thus, equivalent circle diameter is more than the average roundness of the field trash of 1.0 μm
Suitably controlled.Described further below.
First the cool time (t1) of 1450～1500 DEG C of temperature ranges was controlled below 300 seconds.Exceed at above-mentioned t1
When 300 seconds, the generation of the plyability of the secondary inclusion thing with Al system field trash as core is encouraged, and equivalent circle diameter is more than 1.0 μ
The shape of the field trash of m deforms, average roundness becomes big, or above-mentioned B value reduction etc., it is impossible to play desired extremely low temperature
Toughness (with reference to table 2B described later No.34,35).If from the above point of view, t1 is ultrashort the best, preferably less than 290 seconds, more
It is preferably less than 280 seconds.From the above point of view, the lower limit of t1 is not particularly limited.
It addition, in the present invention, why the temperature range when casting in this, concentrates particularly on the temperature of 1450～1500 DEG C
Degree scope, is solidification during owing to casting in this temperature range, carries out composition and causes field trash to the thickening of steel-making
The temperature province that is promoted of growth.
Additionally, the temperature range of above-mentioned 1450～1500 DEG C refers to the temperature of the central part (t/2) of slab thickness t.Its reason
As described below.As it was previously stated, the secondary inclusion thing mainly composition generation in liquation of oxidation system, it is therefore necessary to control liquation portion
Cool time.But, 1450～1500 DEG C owing to carrying out the temperature field solidified the most simultaneously, therefore according to temperature measuring position
Difference, there is in mensuration the probability solidifying, cannot correctly measuring the cool time in liquation portion.Therefore, in the present invention
Measure until lowest temperature there is also the cool time of the t/2 position of liquation.The temperature of the central part that slab is thick can be by by heat
Galvanic couple inserts and measures in mold.
Secondly, control to be less than 680 seconds by the cool times of 1300～1200 DEG C (t2).If above-mentioned t2 was more than 680 seconds, then
The most sulfide-based secondary inclusion thing is encouraged to the composition generation of Al system field trash, the average roundness of above-mentioned field trash
Still become big (with reference to the No.36 of table 2B described later).From the above point of view, t2 is the shortest, is more obtained in that the folder close to positive round
Foreign material, are therefore useful.Preferably t2 is less than 650 seconds, more preferably less than 600 seconds.But, if t2 is too short, cool down burden
Increasing, therefore practical upper recommendation is set to more than about 400 seconds.
It should be noted that the temperature range of above-mentioned 1300～1200 DEG C refers to the temperature of 1/4 (t/4) of slab thickness t.
It reason for this is that, the cool time of 1300～1200 DEG C is main in solid iron sulfide-based the two of composition generation for controlling
Secondary field trash, in said temperature territory, solidification has been basically completed, and therefore measures at the t/4 carrying out brittle fracture rate mensuration
The cool time of position.The temperature in the t/4 portion that slab is thick can measure by being inserted in mold by thermocouple.
In the present invention, if as described above to the cool time (t1) within the temperature range of 1450～1500 DEG C and
The cool time (t2) of 1300～1200 DEG C of In is controlled, and does not limit its means.Such as, about t1, can be for
This temperature range cools down with the average cooling rate of constant speed, less than about 0.17 DEG C/sec, so that in the range of said temperature
Cool time is less than 300 seconds, or can also be cooled down by different rate of cooling, so that said temperature scope is cold
But the time is less than 300 seconds.T2 is too.
It addition, in the present invention, the cooling means for temperature range during casting beyond said temperature scope does not has
Any restriction, it is possible to use usual way (air cooling or water-cooled).
In the above described manner after casting, carry out hot rolling, for heat treatment.
Here, hot-rolled process is not particularly limited, it is possible to use conventional method to obtain the thickness of slab of regulation, concrete and
Speech, can regulate (finish to gauge) temperature, drafts etc. after being heated 1～4 hour at about 1100 DEG C by slab.
After hot rolling, it is heated to the temperature range (TL) of Ac1～Ac3 point, after holding, carries out water-cooled.This process is equivalent to
L process described in aforesaid prior art, thereby, it is possible to the residual γ of stable existence is in the scope of ormal weight at guaranteeing-196 DEG C
In.
In detail, two phase regions [ferrite (α)-γ] temperature (TL) of Ac1～Ac3 point it is heated to.By being heated to this
Temperature province, in the γ phase generated, the alloying element of Ni etc. concentrates, it is possible at room temperature obtain the quasi-steady that quasi-steady exists
Residual γ phase.Less than Ac1Put or more than Ac3During point, result is that the residual γ phase at can not substantially ensuring that-196 DEG C is (with reference to aftermentioned
The No.37 of table 2B, 38).Preferably heating-up temperature substantially 660～710 DEG C.
Heat time heating time (retention time, tL) at a temperature of above-mentioned two phase regions, preferably approximately 10～50 minutes.Less than 10 points
Zhong Shi, alloying element is the most fully carried out to the concentration of γ phase, and on the other hand, during more than 50 minutes, α phase is annealed, and intensity reduces.Excellent
The substantially 15～30 minutes heat time heating time of choosing.
In addition it is more than 15 minutes by making above-mentioned heat time heating time, so that it is guaranteed that the volume integral of the residual γ phase at-196 DEG C
Rate is more than 4.0%, and thus, the brittle fracture rate at will ensure that-233 DEG C is less than 50%, even and if lower extremely low
Good toughness is can also ensure that under temperature.It should be noted that the upper limit of preferred heat time heating time same as described above (30 minutes with
Under).
Then, after water-cooled to room temperature, temper is carried out.Temper is at 520 DEG C～Ac1The temperature range (T3) of point is entered
Row 10～60 minutes (t3).Thus, during tempering, C is concentrated in quasi-steady residual γ, and the degree of stability of quasi-steady residual γ phase increases,
Therefore, it is possible to obtain the residual γ phase of also stable existence at-196 DEG C.If temperature T3 is lower than 520 DEG C, then coexist in two-phase
The quasi-steady residual γ phase decomposition that territory generates in keeping becomes α phase and cementite phase, it is impossible to residual γ at substantially ensuring that-196 DEG C
Phase (with reference to the No.41 of table 2 described later).On the other hand, temperature T3 is more than Ac1Point, or tempering time t3 was less than 10 minutes
Time, C concentration in quasi-steady residual γ phase cannot fully be carried out, it is impossible to guarantees the residual γ amount [ginseng at desired-196 DEG C
No.55 (example that t3 is short) according to table 2 described later].If it addition, tempering time t3 was more than 60 minutes, then the residual at-196 DEG C
γ phase generates superfluously, it is impossible to guarantee the intensity (with reference to the No.43 of table 2 described later) of regulation.
Preferably temper condition is, temperature T3:570～620 DEG C, more than tempering time t3:15 minute, 45 points
(more preferably less than 35 minutes, more preferably less than 25 minutes) below clock.
After carrying out temper as described so, it is cooled to room temperature.Cooling means is not particularly limited, and air cooling or water-cooled are equal
Can.
In this manual, (" 4 ferrum steel compiled by the metallography material in lecture modern times based on following formula calculating for Ac1 point and Ac3 point
Material ", from the metallography meeting of Japan of civic organization).
Ac1 point
=723-10.7 × [Mn]-16.9 × [Ni]+29.1 × [Si]+16.9 × [Cr]+290 × [As]+6.38 × [W]
Ac3 point
=910-203 × [C]1/2-15.2×[Ni]+44.7×[Si]+104×[V]+31.5×[Mo]+13.1×[W]
In above-mentioned formula, [] meaning is the concentration (quality %) of the alloying element in steel.It should be noted that in the present invention
In, do not contain As and W as composition in steel, therefore in above formula, [As] and [W] all calculates as 0%.
Embodiment
Hereinafter, enumerate embodiment and further illustrate the present invention, but the present invention is not limited by following embodiment, can be at energy
Enough meeting and changed in the range of objective aforementioned, described later and implement, these are all contained in the range of the technology of the present invention.
Embodiment 1
Using vacuum fusion stove (150kgVIF), with the melting condition shown in table 2, the one-tenth shown in melting table 1 is grouped into (remaining
Amount: ferrum and inevitable impurity, unit is quality %) for examination steel, after casting, by forge hot, make 150mm ×
The ingot bar of 150mm × 600mm.In the present embodiment, use containing Ce about 50%, the mischmetal of La about 25% as REM.Separately
Outward, the order of addition of deoxidant element, when without selection component, for Si, Mn (adding) → Al simultaneously；On the other hand, containing
During the selection component of Ti, REM, Zr, Ca, for Si, Mn (adding) → Al → Ti → REM, Zr, Ca (adding) simultaneously simultaneously.Need
Illustrate, in the present embodiment, add, from Al, time all about 10 minutes (not the showing table) started to casting.
It addition, in table 2, [O] is the soluble oxygen content (ppm) before Al adds, t1 is the cold of 1450～1500 DEG C during casting
The cool time (second) of 1300～1200 DEG C when but time (second), t2 are to cast.The cooling of each temperature field is by air cooling or water
Cold to be controlled above-mentioned cool time.
Then, for above-mentioned ingot bar, after 1100 DEG C of heating 1～4 hour, it is rolling to plate with the temperature of more than 830 DEG C
Thick 75mm, water-cooled after rolling with final rolling temperature 780 DEG C, thus obtain the steel plate of thickness of slab 25mm.To thus obtain
To steel plate be heated to the temperature (in table 2, TL) shown in table 2 after, after heating keeps 5～60 minutes (with reference to the tL of table 2), water-cooled
To room temperature.Then, after carrying out temper (T3=temperature, t3=tempering time) as shown in table 2, air cooling or water-cooled are carried out
To room temperature.
For thus obtained steel plate, evaluate the flat of the equivalent circle diameter field trash more than 1.0 μm as follows
All roundness A (individual/mm2),-196 DEG C exist the volume fraction (%) of residual γ phase, tensile characteristics (tensile strength TS,
Yield strength YS), pole low-temperature flexibility (the brittle fracture rate in the C direction at-196 DEG C or-233 DEG C).
(1) equivalent circle diameter mensuration more than the average roundness A of the field trash of 1.0 μm
The t/4 position (t: thickness of slab) of above-mentioned steel plate is carried out mirror ultrafinish, uses optical microscope with 400 times for 4
Visual field shooting photo.Further, the area in each visual field is 0.04mm2, the total area in 4 visuals field is 0.15mm2.For this 4
Viewed field trash in the individual visual field, carries out image by Media Cybernetics society's system " Image-ProPlus " and divides
Analysis, based on following formula calculating equivalent circle diameter (diameter) more than the roundness of the field trash of 1.0 μm, is averaged value as above-mentioned folder
The average roundness A of foreign material.At field trash when being shaped as positive round, the roundness calculated by following formula is 1.The shape of field trash
Deforming the most serious, the value of the roundness calculated by following formula is the biggest.
Roundness=L2/4π/S
In formula, area (the unit μm that surrounding head (unit μm) that L is field trash, S are field trash2)。
It should be noted that in the present embodiment, equivalent circle diameter observes about 200～300 more than the field trash of 1.0 μm
Individual/mm2Left and right.
(2) in the mensuration of the volume fraction-196 DEG C of residual γ phases existed
From the t/4 position of each steel plate, extract the test film of 10mm × 10mm × 55mm, keep with liquid nitrogen temperature (-196 DEG C)
After 5 minutes, carry out X-ray diffraction survey with two dimension small portion X-ray diffraction device (RINT-RAPIDII) of リ ガ Network company
Fixed.Then, about (110), (200), (211) of ferritic phase, the peak value of each lattice plane of (220) and residual γ phase
(111), (200), (220), the peak value of each lattice plane of (311), integrated intensity ratio based on each peak value, calculate residual γ respectively
(111), (200), (220) of phase, the volume fraction of (311), try to achieve its meansigma methods, as " the volume fraction of residual γ
(%) ".
(3) mensuration of tensile characteristics (tensile strength TS, yield strength YS)
From the t/4 position of each steel plate, and No. 4 test films that JIS Z2241 is extracted in C direction abreast, with JIS Z2241 institute
The method stated carries out tensile test, measures tensile strength TS and yield strength YS.In the present embodiment, TS ＞ 690MPa, YS ＞
590MPa's, it is evaluated as strength of parent excellent.
(4) mensuration of pole low-temperature flexibility (the brittle fracture rate in C direction)
From the t/4 position (t: thickness of slab) of each steel plate and W/4 position (W: plate width), and t/4 position and W/2 position, with C side
Charpy-type test sheet (the V notch test sheet of JIS Z2242) 3 is extracted to abreast, with the method described in JIS Z2242,
Brittle fracture rate (%) at measuring-196 DEG C, calculates respective meansigma methods.Then, two meansigma methodss so calculated it
In, using the meansigma methods of (that is, brittle fracture rate is big) side of characteristic difference, this value is less than 10%, in the present embodiment
It is evaluated as pole excellent in low temperature toughness.
These results are recorded in table 2 in the lump.For reference, in Tables 1 and 2, note has Ac1 point and Ac3 point in the lump.
[table 1A]
[table 1B]
[table 2A]
[table 2B]
Following investigation can be carried out by table 2.
First, the No.1～32 of table 2A is the example fully meeting inventive feature, using the teaching of the invention it is possible to provide though strength of parent
Height, the still excellence of the pole low-temperature flexibility (being exactly meansigma methods≤10% of the brittle fracture rate in C direction in detail) at-196 DEG C
Steel plate.
In contrast, the No.33 of table 2B～41,43,55, at least it is unsatisfactory for preferred manufacturing condition any of the present invention
One, it is the comparative example being unsatisfactory for inventive feature, therefore can not get desired characteristic.
Specifically, although No.33 employs the No.33 that composition in steel meets the table 1B of inventive feature, but Al
Soluble oxygen content [O] amount before interpolation is many, is therefore the example of the average roundness A increase of above-mentioned field trash.As a result of which it is, fragility
Fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
Although No.34 employs the No.34 that composition in steel meets the table 1B of inventive feature, but during casting 1500～
The cool time (t1) of 1450 DEG C is long, is therefore the B value example less than the scope of regulation.As a result of which it is, brittle fracture rate increases,
Desired pole low-temperature flexibility can not be realized.
No.35 measures the No.35 of many table 1B because of use P, and, the cool time of 1500～1450 DEG C during casting
(t1) long, so being the example of the average roundness A increase of above-mentioned field trash.As a result of which it is, brittle fracture rate increases, it is impossible to real
Existing desired pole low-temperature flexibility.
No.36 measures the No.36 of many table 1B because employing C, and, the cool time of 1300～1200 DEG C during casting
(t2) long, so being the example of the average roundness A increase of above-mentioned field trash.As a result of which it is, brittle fracture rate increases, it is impossible to real
Existing desired pole low-temperature flexibility.
Although No.37 employs the No.37 that composition in steel meets the table 1B of inventive feature, but with less than two-phase
The temperature heating of territory temperature (TL), so being the example that residual γ amount is not enough.As a result of which it is, brittle fracture rate increases, it is impossible to real
Existing desired pole low-temperature flexibility.
No.38 measures the No.38 of many table 1B because employing Si, and, add with the temperature more than two phase region temperature (TL)
Heat, so being the example that residual γ amount is not enough.As a result of which it is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
Although No.39 employs the No.39 that composition in steel meets the table 1B of inventive feature, but two phase region temperature (TL)
Under heated hold time (tL) short, be therefore the example that residual γ amount is not enough.As a result of which it is, brittle fracture rate also increases, no
Desired pole low-temperature flexibility can be realized.
Although No.40 employs the No.40 that composition in steel meets the table 1B of inventive feature, but in two phase region temperature
(TL) heated hold time (tL) is long, is therefore the example of residual γ amount increase.As a result of which it is, yield strength YS and tension are strong
Degree TS reduces, it is impossible to guarantee desired strength of parent.
Although No.41 employs the No.41 that composition in steel meets the table 1B of inventive feature, but temperature (T3)
Low, therefore it is the example that residual γ amount is not enough.As a result of which it is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
Although No.43 employs the No.43 that composition in steel meets the table 1B of inventive feature, but tempering time (t3)
Long, so being the example of residual γ amount increase.As a result of which it is, yield strength YS reduces, it is impossible to guarantee desired strength of parent.
Although No.55 employs the No.55 that composition in steel meets the table 1B of inventive feature, but tempering time (t3)
Short, therefore it is the example that residual γ amount is not enough.As a result of which it is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.42,44～54 be the use of only in steel composition depart from, the comparative example manufactured with the inventive method.
In detail, No.42 is the use of the No.42 of the many table 1B of Mn amount, the example that therefore residual γ amount is not enough.Its knot
Fruit is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.44 is the No.44 employing the few table 1B of Mn amount, the example that therefore residual γ amount is not enough.As a result of which it is, fragility
Fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.45 is the example of the No.45 of the table 1B that use S amount is many.Therefore, brittle fracture rate increases, it is impossible to realize wishing
Pole low-temperature flexibility.
No.46 is the No.46 of the table 1B that C measures less, Al amount is many, Ni amount is few, and the average roundness A of the most above-mentioned field trash increases
Add, remain the example that γ amount is not enough.As a result of which it is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.And then,
TS also reduces.
No.47 is the No.47 of the table 1B that use Al measures less, N amount is many, and the average roundness A of the most above-mentioned field trash increases
Example.As a result of which it is, brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.48 is the example of the No.48 employing the table 1B that the Cu as selection component measures and Ca amount is many.As a result of which it is,
Brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.49 is the example of the No.49 employing the table 1B that the Cr as selection component measures and Zr amount is many.As a result of which it is,
Brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.50 is the example of the No.50 employing the table 1B that the Nb as selection component measures and REM amount is many.As a result of which it is,
Brittle fracture rate increases, it is impossible to realize desired pole low-temperature flexibility.
No.51 measures the No.51 of many table 1B owing to employing the Mo as selection component, and therefore brittle fracture rate increases,
Desired pole low-temperature flexibility can not be realized.
No.52 measures the No.52 of many table 1B owing to employing the Ti as selection component, and therefore brittle fracture rate increases,
Desired pole low-temperature flexibility can not be realized.
No.53 measures the No.53 of many table 1B owing to employing the V as selection component, and therefore brittle fracture rate increases, no
Desired pole low-temperature flexibility can be realized.
No.54 is to employ the B as selection component to measure the No.54 of many table 1B, and therefore brittle fracture rate increases, it is impossible to
Realize desired pole low-temperature flexibility.
Embodiment 2
In the present embodiment, for for the data of the part of above-described embodiment 1 (being example of the present invention) ,-233 are evaluated
DEG C brittle fracture rate.
Specifically, for the No. (No. of the corresponding aforesaid Tables 1 and 2 of the No. of table 3) described in table 3, from t/4 position
And W/4 position extraction test film 3, implement the Charpy-type test of-233 DEG C with method as described below, evaluate brittle fracture
The meansigma methods of rate.In the present embodiment, above-mentioned brittle fracture rate≤50%, the brittle fracture rate being evaluated as-233 DEG C is excellent.
" gases at high pressure ", volume 24 page 181, " the extremely low temperature impact test of austenite stainless steel cast steel "
These results are recorded in table 3.
Table 3
[table 3]
The No.3 of table 3,4,6,15,19 and 24, be all by two phase regions at a temperature of heated hold time (tL) control 15
Example (with reference to table 2A) more than minute, it can be ensured that residual γ phase is more than 4.0%.As a result of which it is, not only at-196 DEG C, more
The brittle fracture rate of-233 DEG C of low temperature is the best, it is possible to reach the most excellent pole low-temperature flexibility.
Illustrate the present invention in detail and with reference to particular implementation, but skilled person will appreciate that, can be not
Depart from the range of the spirit and scope of the present invention in addition various changes and modifications.
The Japanese patent application (Patent 2012-184593) that the application proposed based on August 23rd, 2012, its content conduct
With reference to introducing here.
Usability in industry
The steel plate pole excellent in low temperature toughness of the present invention, especially as storage tank and the cargo ship of liquefied natural gas (LNG)
Deng steel useful.
Claims (3)
1. the steel plate of a pole excellent in low temperature toughness, it is characterised in that
Described steel plate contains in terms of quality %:
C:0.02～0.10%,
Below Si:0.40% but without 0%,
Mn:0.50～2.0%,
Below P:0.007% but without 0%,
Below S:0.007% but without 0%,
Al:0.005～0.050%,
Ni:5.0～7.5%,
Below N:0.010% but without 0%,
Surplus is ferrum and inevitable impurity,
Present in steel plate, equivalent circle diameter is less than 1.8 more than the average roundness A of the field trash of 1.0 μm,
2.0～12.0%, and the B represented by following (1) formula is met at the volume fraction V of-196 DEG C of retained austenite phases existed
Value is more than 1.3,
B=V2/3/A···(1)。
Steel plate the most according to claim 1, wherein, is calculated as with volume fraction at-196 DEG C of retained austenites existed
4.0～12.0%.
Steel plate the most according to claim 1 and 2, wherein,
Possibly together with being selected from terms of quality %
Below Cu:1.00% but without 0%,
Below Cr:1.2% but without 0%,
Below Mo:1.00% but without 0%,
Below Ti:0.025% but without 0%,
Below Nb:0.10% but without 0%,
Below V:0.50% but without 0%,
Below B:0.0050% but without 0%
Below Ca:0.0030% but without 0%,
Below REM:0.0050% but without 0%,
Below Zr:0.0050% but without at least one in 0%.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2012-184593 | 2012-08-23 | ||
| JP2012184593A JP5833991B2 (en) | 2012-08-23 | 2012-08-23 | Thick steel plate with excellent cryogenic toughness |
| PCT/JP2013/072120 WO2014030618A1 (en) | 2012-08-23 | 2013-08-19 | Thick steel plate having good ultralow-temperature toughness |
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| Publication Number | Publication Date |
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| CN104583439A CN104583439A (en) | 2015-04-29 |
| CN104583439B true CN104583439B (en) | 2016-10-12 |
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| CN201380043453.6A Expired - Fee Related CN104583439B (en) | 2012-08-23 | 2013-08-19 | The steel plate of pole excellent in low temperature toughness |
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| Country | Link |
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| EP (1) | EP2889391B1 (en) |
| JP (1) | JP5833991B2 (en) |
| KR (1) | KR101632159B1 (en) |
| CN (1) | CN104583439B (en) |
| WO (1) | WO2014030618A1 (en) |
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| JP6055363B2 (en) * | 2013-04-17 | 2016-12-27 | 株式会社神戸製鋼所 | High strength thick steel plate with excellent cryogenic toughness |
| JP6369003B2 (en) * | 2013-10-09 | 2018-08-08 | 新日鐵住金株式会社 | Steel material and manufacturing method thereof |
| JP6196929B2 (en) * | 2014-04-08 | 2017-09-13 | 株式会社神戸製鋼所 | Thick steel plate with excellent HAZ toughness at cryogenic temperatures |
| EP3276020B1 (en) * | 2015-03-27 | 2020-09-23 | JFE Steel Corporation | High-strength steel plate, production method therefor, steel pipe, and production method therefor |
| JP2017115239A (en) * | 2015-12-18 | 2017-06-29 | 株式会社神戸製鋼所 | Thick steel sheet excellent in ultra low temperature toughness |
| CN105543694B (en) * | 2015-12-29 | 2017-12-29 | 东北大学 | A kind of preparation method of LNG tank 7Ni steel plates |
| JP2018009239A (en) * | 2016-02-15 | 2018-01-18 | 株式会社神戸製鋼所 | Steel sheet and production method therefor |
| KR102364473B1 (en) * | 2017-08-23 | 2022-02-18 | 바오샨 아이론 앤 스틸 유한공사 | Steel for low-temperature pressure vessel and manufacturing method thereof |
| KR102075205B1 (en) | 2017-11-17 | 2020-02-07 | 주식회사 포스코 | Cryogenic steel plate and method for manufacturing the same |
| KR102075206B1 (en) | 2017-11-17 | 2020-02-07 | 주식회사 포스코 | Low temperature steeel plate having excellent impact toughness property and method for manufacturing the same |
| CN109609853A (en) * | 2019-01-14 | 2019-04-12 | 东北大学 | A kind of low-temperature storage tank potassium steel and preparation method thereof |
| KR102200225B1 (en) * | 2019-09-03 | 2021-01-07 | 주식회사 포스코 | Steel Plate For Pressure Vessel With Excellent Lateral Expansion And Manufacturing Method Thereof |
| CN111440990B (en) * | 2020-03-30 | 2022-07-15 | 江阴兴澄特种钢铁有限公司 | Manufacturing method of marine 5Ni steel plate with low remanence and excellent surface quality |
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| JP4872917B2 (en) * | 2005-09-21 | 2012-02-08 | 住友金属工業株式会社 | Low temperature steel and its manufacturing method |
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| JPS5512083B2 (en) | 1973-05-04 | 1980-03-29 | ||
| JPS5113308A (en) | 1974-07-24 | 1976-02-02 | Nippon Steel Corp | TEIONYOKYOJINKOOYOBISONO NETSUSHORIHOHO |
| JPH06184630A (en) * | 1992-12-18 | 1994-07-05 | Nippon Steel Corp | Production of thick 9% ni steel excellent in low temperature toughness |
| JPH09135813A (en) | 1995-11-15 | 1997-05-27 | Canon Inc | Ophthalmic photographing device |
| JP4213833B2 (en) | 1999-10-21 | 2009-01-21 | 新日本製鐵株式会社 | High toughness and high strength steel with excellent weld toughness and manufacturing method thereof |
| JP2004263281A (en) * | 2003-03-04 | 2004-09-24 | Jfe Steel Kk | Method for manufacturing nickel-containing shaped steel of excellent strength and low-temperature toughness |
| JP5223706B2 (en) * | 2009-02-03 | 2013-06-26 | 新日鐵住金株式会社 | Steel material excellent in toughness of heat-affected zone with high heat input and manufacturing method thereof |
| JP5494167B2 (en) * | 2010-04-14 | 2014-05-14 | 新日鐵住金株式会社 | Cryogenic steel plate and manufacturing method thereof |
| JP5494166B2 (en) * | 2010-04-14 | 2014-05-14 | 新日鐵住金株式会社 | Cryogenic steel plate and manufacturing method thereof |
| JP4975888B2 (en) | 2010-07-09 | 2012-07-11 | 新日本製鐵株式会社 | Ni-added steel sheet and manufacturing method thereof |
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2013
- 2013-08-19 EP EP13831371.3A patent/EP2889391B1/en not_active Not-in-force
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|---|---|---|---|---|
| JP4872917B2 (en) * | 2005-09-21 | 2012-02-08 | 住友金属工業株式会社 | Low temperature steel and its manufacturing method |
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| Publication number | Publication date |
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| CN104583439A (en) | 2015-04-29 |
| EP2889391A4 (en) | 2016-05-18 |
| KR20150029754A (en) | 2015-03-18 |
| JP2014040648A (en) | 2014-03-06 |
| KR101632159B1 (en) | 2016-06-20 |
| JP5833991B2 (en) | 2015-12-16 |
| EP2889391B1 (en) | 2017-12-20 |
| WO2014030618A1 (en) | 2014-02-27 |
| EP2889391A1 (en) | 2015-07-01 |
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